Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 250901

Area Forecast Discussion
National Weather Service Marquette MI
501 AM EDT Wed Apr 25 2018

.SHORT TERM...(Today and tonight)
Issued at 343 AM EDT WED APR 25 2018

Shortwave trough that brought brief period of light rain showers to
much of Upper Michigan last evening and early this morning will be
east of Upper Michigan by daybreak this morning. Any rain early
this morning will be confined over APX forecast area to far east
near Drummond Island. Most areas saw well under 0.10 inch with
the precip with the most rain occurring along southwest and south
central Upper Michigan. Area of 2-4kft clouds from eastern Lk
Superior into northern Ontario should expand across mainly east
half of forecast area this morning before scouring out for the
aftn as high pressure and very dry airmass take hold. Expect temps
to exhibit a more typical early spring setup with coolest
readings in the upper 30s/low 40s near Lk Superior due to
lingering gradient northwest winds. Warmest readings in the upper
50s to near 60F will be found near Wisconsin state line. No reason
to stray from previous shift going on the lower end of guidance
for Td today. Expect resulting min RH values to drop to 20-25 pct
inland west. Winds in that area should be diminishing late morning
into the aftn as the high moves closer, limiting any fire weather
concerns where the snow has left.

High pressure drifts overhead tonight with fairly low pwats so
expect temps to be mainly in the 20s. Used the GEM bias corrected
for min temps. Could be colder in the mid to upper teens interior
east where winds stay light all night and could be warmer into the
30s far west as southwest winds start to stir ahead in gradient flow
between the exiting high and cold front moving toward western Lk
Superior. Though there may be increase in high clouds late west, any
precip with the front will hold off til later Thu morning.

.LONG TERM...(Thursday through Tuesday)
Issued at 458 AM EDT WED APR 25 2018

Models suggest that a progressive pattern will prevail as the
mid/upper level trough into the cntrl CONUS shifts to the ne CONUS
this weekend and a ridge builds into the cntrl CONUS downstream from
a trough advancing into the wrn CONUS. After a brief warmup
Thursday, cooler weather will move in Fri/Sat before a substantial
warming trend from Sunday into early next week.

Thursday, similar to the scenario late Tuesday, after warming into
the upper 50s to lower 60s, another shortwave trough and associated
850-700mb fgen will advance through Upper Michigan in the afternoon
and evening. However, since the forcing is stronger, the fcst
includes higher chance POPs/QPF, especially over the west half and
far south. Enough colder air will move in during the evening for
some of the rain to change over to snow.

Friday, a compact vigorous clipper shortwave will drop se through
Upper Michigan bringing another round of mainly light pcpn. An
area of strong mid level fgen along with steep 700-500 mb lapse
rates of 7- 8C/km will support snow or rain showers changing to
mainly rain. Although there may be a brief period of heavier pcpn
with this feature overall QPF of mainly 0.05 inch or less is

Saturday, high pressure building into the area will bring clearing
but northerly flow will maintain the cool air across the region and
keep highs in the low 40s north to low 50s south.

Sunday through Tuesday, a transition to low/mid level sw flow will
bring very warm air to the norther Great Lakes with highs into the
70s to possibly 80 by Mon/Tue. Moisture advection pushing dewpoints
to near 50 will also provide enough instability for the mention of
tsra by Tue with the approach of a shortwave trough and cold front
as low pressure lifts to the nw of the region. There is still plenty
of uncertainty with the details of any weaker shrtwvs moving out of
the plains and the impact on pcpn chances/amounts. Although some sct
pcpn amounts to near 0.50 inch may be possible, the signal for any
widespread heavier rain is lower.

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 140 AM EDT WED APR 25 2018

Some stratocu will pass across KCMX and especially KSAW overnight
into the morning. Cloud bases are likely to range from 3500-5000ft,
but there is a small chance MVFR cigs could occur at KSAW so have
included tempo group. May also see shallow ground fog at KIWD toward
sunrise. Any fog and low clouds will clear out this morning as a dry
air mass overspreads the area, ensuring VFR conditions prevail at
KIWD/KCMX/KSAW today thru this evening.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 343 AM EDT WED APR 25 2018

Northwest winds 20-25 knots, strongest over central and eastern Lake
Superior, diminish to southwest 15 kts or less later this afternoon
into tonight. Cold front crossing Lk Superior on Thu will swing
winds back to the northwest and could see gusts reach 30 kts Thu
afternoon especially north central and eastern Lk Superior. Winds
diminish to 15 kts or less Fri into Sat before increasing from the
southwest 20-25 kts Sun into Mon as strong low pressure system
tracks across northern Plains.

Issued at 458 AM EDT WED APR 25 2018

After a 24-hour period of highs in the lower 70s and lows in the low
to mid 30s (e.g. above freezing), the snow pack has lost 3-5 inches
across much of Upper Michigan.  The snow pack will continue to melt
but at a slower pace mostly driven by the sun (when not blocked by
clouds). Most rivers across Upper Michigan have seen manageable
rises in water levels thus far, except for a minor ice jam reported
on the Ford river in Escanaba that has since broken apart.
Precipitation chances over the next several days look somewhat bleak
(collectively less than 0.25"). However, temperatures next week will
increase dramatically with an accompanying increase in moisture,
likely leading to a rapid decrease in snow cover across the area.
There are indications of heavier precipitation toward the middle to
end of next week, though uncertainly remains on exactly where and
how much will fall. All in all, the snow pack is expected to shrink
considerably next week which may lead to minor river flooding in the
usual rivers prone to spring flooding.

Upper Michigan...
Lake Superior...
Lake Michigan...


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